what is retrospective validation , give brief.

From the WHO: Involves the evaluation of past experience of production on the condition that composition, procedures, and equipment remain unchanged.

From PIC’s: There are many processes in routine use in many companies that have not undergone a formally documented validation process.
Validation of these processes is possible, using historical data to provide
the necessary documentary evidence that the process is doing what it is
believed to do. The steps involved in this type of validation still require
the preparation of a protocol, the reporting of the results of the data
review, leading to a conclusion and recommendation.

This type of validation exercise is only acceptable for well established
processes and will be inappropriate where there have been recent
changes in the composition of the product, operating procedures or
The source of data for this validation may include batch documents,
process control charts, maintenance log books, records of personnel
changes, process capability studies (reflected in a CpK),finished product
data, including trend cards, and storage stability results.

Hope this is of some help.

dear sir

how many batches required for retrospective process validation,is there there any time/ period limit to collecting trend , supporting guide line please